Variable-area nozzle seal

ABSTRACT

This variable-area nozzle vane seal consists of a slot extending from side-to-side of a vane and from a point adjacent the leading edge to another near the overlap of the vanes when in reduced nozzle area positions. This slotting establishes in effect labyrinth seals between the sides of the vanes and the air passage in which they are disposed. The seal is further improved by drilled holes establishing communication between the slots mentioned above and the spaces between adjacent vanes. Airflow through the spaces causes reduced pressure in the slots and leakage is collected and added to flow through the nozzle to assist turbine operation.

United States Patent Gammill et al.

VARIABLE-AREA NOZZLE SEAL Inventors: Edward L. Gamrnill, Phoenix; Nick M.

Hughes; James A. Rhoden, both of Scottsdale, all of Ariz.

The Garrett Corporation, Los Angeles, Calif.

Filed: Oct. 19, 1970 Appl. No.: 82,023

Assignee:

References Cited UNITED STATES PATENTS ,rllllllll i ll ll l vi i H Weber ..4l5/164 Swearingen ..4 15/1 63 FOREIGN PATENTS OR APPLICATIONS 971,548 9/1964 Great Britain ..4l5/ l 63 Primary Examiner-Henry F. Raduazo Attorney-Herschel C. Omohundro and John N. Hazelwood This variable-area nozzle vane seal consists of a slot extending from side-to-side of a vane and from a point adjacent the leading edge to another near the overlap of the vanes when in reduced nozzle area positions. This slotting establishes in effect labyrinth seals between the sides of the vanes and the air passage in which they are disposed. The seal is further improved by drilled holes establishing communication between the slots mentioned above and the spaces between adjacent vanes. Airflow through the spaces causes reduced pressure in the slots and leakage is collected and added to flow through the nozzle to assist turbine operation.

ABSTRACT 7 Claims, 5 Drawing Figures VARIABLE-AREA NOZZLE SEAL SUMMARY This invention relates generally to variable-area nozzles and is more particularly directed to an improvement in such elements used in fluid turbines of the radial inflow type. Still more particularly this invention is directed to an improvement in the variable-area nozzle device shown and described in U.S. Pat. No. 3,101,926, issued Aug. 27, I963 to Fritz Weber and assigned to the assignee of the present application.

As in the above-mentioned patent the fluid turbine herein has a variable-area nozzle structure comprising a plurality of airfoil blades arranged in an annular inlet opening between an inlet fluid manifold'and the periphery of a centripetal turbine wheel. In'the patent the blades are provided with slots in sides adjacent the walls of the annular inlet opening and sealing strips are disposed in the slots for movement under fluid pressure into wiping engagement with slot sidewalls. The use of these sealing strips is objectionable because of the introduction of friction, sticking, leakage, and the multiplicity of parts.

An object of this invention is the elimination of parts and improvement in efficiency of the turbine through the use in each blade of a particular arrangement of slots alone or in combination with one or more drilled holes. It has been discovered that by providing the forward portions of the nozzle blades or vanes with slots extending therethrough from side to side the fluid pressure tends to center the blades in the inlet opening and minimizes leakage of fluid past the blades.

The thin film of fluid between the sides of the blades and the sidewalls of the inlet opening also has a tendency to reduce the To provide the variable area inlet nozzle for the turbine, ring member 22 has a plurality of circumferentially spaced openings 25 formed therein for the rotatable reception of shafts 26 having disks 27 adjacent one end and recessed in the sidewall of the annular inlet opening. Each disk 27 has a blade or vane 28 integrally formed therewith, the blades or vanes 28 being, in the form of the invention illustrated, of curved airfoil shape. The vanes are disposed in the annular inlet opening between the sidewalls formed by the members 22 and 23. At the other ends, shafts 26 are provided with lever arms 30 the outer ends of which have slots 31 for receiving pins 32 carried by an actuator ring 33. This ring is supported for limited rotary movement on grooved rollers 34 in response to suitable adjusting mechanism, now shown. It will be apparent from FIG.

friction and decrease the force necessary to effect the adjustment of the blades.

Another object of the invention is to provide the slotted blades mentioned in the preceding paragraph with one or more holes establishing communication between the slot and the back or convex side of the blade whereby the slot may be vented to the nozzle passage and the fluid which would normally be unused as leakage will be added to the fluid flowing through the nozzle and applied to the wheel blades.

Other objects 'will be apparent from the following description of one form of the invention selected for illustration in detail in the accompanying drawing.

IN THE DRAWING FIG. 1 is a partial axial sectional view taken through a fluid turbine provided with a variable area nozzle structure formed in accordance with the present invention;

FIG. 2 is a detail transverse sectional view on a larger scale taken through the variable area nozzle structure on the plane indicated by the line lI-II of FIG. 1;

FIG. 3 is a perspective view of a variable-area nozzle blade embodying the invention;

FIG. 4 is a sectional view taken through the nozzle blade on the plane indicated by the line IV-IV of such figure; and

FIG. 5 is a similar view taken through a modified form of the invention.

Closer reference to the drawing and particularly FIG. 1 will show that a fluid pressure operated turbine of the type selected for illustration includes a frame structure 11 in which a shaft 12 is joumaled as at 13 for rotation. One end of the shaft is equipped with a centripetal turbine wheel 14 having a plurality of blades 15 radiating from a hub 16. The blades are spaced to provide fluid channels 17 which enter the wheel from the periphery and exit axially due to the curvature of the hub surface 18 and outer shroud 20. The latter element is of annular construction and provides a center exhaust outlet 21.

The frame structure 11 has a pair of ring members 22 and 23 secured thereto, suitable bosses 24 serving to maintain members 22 and 23 in spaced relation to provide an annular inlet opening in radial registration with the periphery of the wheel 14, one side of each of members 22 and 23 providing a side wall of such opening. Shroud 20 is integrally formed with member 23.

2 that when ring 33 is moved about the axis of the turbine wheel, arms 30 will in turn impart rotary adjustment to shafts 26 and consequent movement of vanes 28 about the axes of their respective shafts. This movement varies the area of nozzle passages formed between adjacent vanes and obviously will vary the flow of fluid under pressure from the inlet manifold 34 formed by frame part 35 which surrounds the inlet opening, to the turbine wheel.

The feature of this invention is the formation of each blade or vane 28 with a slot 36 which extends from side to side of the portion of the blade that projects forwardly beyond the disk 27. This slot is similar to the slots formed in the vanes of U.S. Pat. No. 3,101,926 mentioned above, for the reception of sealing strips. However, in the present application, the sealing strips are omitted and the slots 36 extend straight through the vanes 28 in the first form illustrated or they may be of limited depth as shown at 37 in FIG. 5 and connected by one or more passages 38. As shown more particularly in FIGS. 4 and 5, the slots 36 and 37 communicate with the space between adjacent vanes by way of one or more holes 40 extending toward the trailing edge of the vane. In the curved airfoil shaped vane illustrated the holes open to the convex side of the blade a short distance in advance of the trailing edge 41. The slots 36 and 37 extend to points in close proximity to the vane leading edge 42.

In the operation of the fluid turbine, air or other fluid under pressure, is supplied from a suitable source to the manifold 34 and flows, see arrows in FIG. 1, to the annular inlet opening between ring members 22 and 23. Such air then passes through the nozzle spaces between adjacent vanes 28 and into channels 17 between blades 15 on the turbine wheel. As should be obvious from the drawing and the description above, the area of the nozzle spaces may be varied through the adjustment of vanes 28 by rotary manipulation of ring 33.

The efficiency of the device depends, in part, upon the control of leakage of fluid under pressure from manifold 34 between the vanes 28 and ring members 22 and 23 to the chamber containing turbine wheel 14, particularly when the vanes 28 are positioned to provide small nozzle areas. In this case leakage is controlled by the arrangement of the slots 36 or 37 and holes 38 and 40. It is theorized that when the vanes 28 are disposed to provide small nozzle areas fluid leakage between the side edges of the vanes and the adjacent surfaces of the rings 22 and 23 will be opposed by the labyrinth seal effect provided by the edges of the vanes at the slots 36. In addition, it is believed that the flow of fluid through the reduced nozzle areas tends to cause fluid flow from the slots 36 or 37 through holes 40 creating a reduced pressure in such slots. Because of this pressure reduction fluid tending to leak past the sides of the vanes will be collected by the slots 36 or 37 and combined with fluid flowing through the noule openings to assist in effecting rotation of the turbine.

Actual tests of turbines with variable area nozzle vanes embodying the sealing means of the invention have shown a considerable increase in efficiency over prior constructions.

We claim:

1. Sealing means for a variable-area nozzle of the type having a passageway defined by a pair of spaced walls and a plurality of airfoil-shaped nozzle vanes with leading and trailing m7 Mledges supported between said walls for adjustment about spaced axes extending transversely of the passageway and substantially normal to the surfaces of said walls to control the flow of fluid under pressure from an inlet plenum to a point of use, comprising:

a. means forming a slot on each side of each nozzle vane adjacent the walls defining the passageway; and v b. means in each vane establishing communication between the slots at the sides thereof.

2. Sealing means as defined in claim 1 in which the slot formed by the first means extends from one side to the other in each vane.

3. Sealing means as defined in claim 1 in which the slot formed by the first means extends a predetermined distance along the vane from a point adjacent the vane leading edge.

4. Sealing means as defined in claim 1 in which the firstmentioned means forms a slot extending a predetermined distance into the vanes at each side thereof and the secondmentioned means includes at least one passage connecting the slots at the sides of the vanes.

5. Sealing means as defined in claim 1 in which means are provided to establish communication between the slots in the vanes and the spaces between adjacent vanes a predetermined distance in advance of the vane trailing edges.

6. Sealing means as defined in claim 2 in which at least one drilled passage extends from the rear end of the slot in each vane to one of the nozzle forming surfaces of the vane at a point disposed in predetermined relation to the vane trailing edge.

7. Sealing means as defined in claim 2 in which each vane is provided with a disk concentric with the axis of adjustment of the vane and the slot formed by the first means extends from a point adjacent the vane leading edge to another point adjacent the edge of said disk. 

1. Sealing means for a variable-area nozzle of the type having a passageway defined by a pair of spaced walls and a plurality of airfoil-shaped nozzle vanes with leading and trailing edges supported between said walls for adjustment about spaced axes extending transversely of the passageway and substantially normal to the surfaces of said walls to control the flow of fluid under pressure from an inlet plenum to a point of use, comprising: a. means forming a slot on each side of each nozzle vane adjacent the walls defining the passageway; and b. means in each vane establishing communication between the slots at the sides thereof.
 2. Sealing means as defined in claim 1 in which the slot formed by the first means extends from one side to the other in each vane.
 3. Sealing means as defined in claim 1 in which the slot formed by the first means extends a predetermined distance along the vane from a point adjacent the vane leading edge.
 4. Sealing means as defined in claim 1 in which the first-mentioned means forms a slot extending a predetermined distance into the vanes at each side thereof and the second-mentioned means includes at least one passage connecting the slots at the sides of the vanes.
 5. Sealing means as defined in claim 1 in which means are provided to establish communication between the slots in the vanes and the spaces between adjacent vanes a predetermined distance in advance of the vane trailing edges.
 6. Sealing means as defined in claim 2 in which at least one drilled passage extends from the rear end of the slot in each vane to one of the nozzle forming surfaces of the vane at a point disposed in predetermined relation to the vane trailing edge.
 7. Sealing means as defined in claim 2 in which each vane is provided with a disk concentric with the axis of adjustment of the vane and the slot formed by the first means extends from a point adjacent the vane leading edge to another point adjacent the edge of said disk. 